Slash 4x4 LCG Stage 2: Initial Design

As for the design, I would be lying to you if I said we didn’t take a look and studied what is currently available on the market.I spent countless hours searching all over the net and forums before we inked our first design.One thing I noticed was that I haven’t seen one that’s “truly” LCG.Some I see the battery and motor was laid down on the chassis, but yet the servo is up on the upper deck.Some I see the battery and servo laid down on the chassis, but yet the motor was up in the original position of the stock Slash 4x4 chassis.We tried our first drawing with the servo in the stock location where it would be secured to the upper deck, just to see what that would look like and try to figure out any advantages of having it high up.

Right away I was not satisfied with what I saw, because in my mind, I want this LCG conversion kit to have everything low to the chassis, and having the servo up on the uppder deck just doesn't look right to me. And we could not identify any advantages to having the servo up high other than it is easier for locating the servo position in relation to the chassis and steering bellcrank.Because the servo is sitting off to one side, while I have no exact computation numbers, but I’m certain the weight bias is off on the front of the truck heavily to one side and thus affecting the feel of steering right versus left.To have the motor up where the stock position is was simply out of the equation.A 550 size motor weighs 5 ounce + and to have that much weight up high is versus now a low CG chassis it just seems counter intuitive.Our primary goal now is very simple:Everything has to be flat and as low as possible to the chassis.

The second revision came back much closer along the line of what I was envisioning, and now we start getting into refining specifics:

1) 4mm lower aluminum chassis.Because of how long the driveshaft is on the Slash 4x4, the 4mm thick aluminum chassis will offer a solid backbone that prevents the chassis from “bowing” and possibly bending the center shaft.We could have easily selected graphite as the lower deck, but here’s my concern with graphite:I raced with graphite chassis cars for over 10 years in touring car racing, and it is light weight, it is strong, but in my opinion as a material for chassis, it has one problem:it can loose its internal structural integrity.Graphite is weaved material, layers on top of layers to form a graphite plate of desire thickness and then cut to the shape of its application.You can take a hard hit and the chassis might look fine on the outside….however, you will never know if the weaves inside are still structurally intact.I’ve had a few occasions where I suffered a massive shunt with my touring cars and although the graphite chassis looks fine from the outside, I’ll usually pick up a mysterious “tweak” in the car (car is responding inconsistently especially left/right turns) that can’t be rectified through suspension tuning.This usually mean it’s time for a new chassis.However, that was in on-road racing where crashes don’t happen that often, but in off-road, you are “crashing” that chassis just about every lap:over the double jumps, the big triple jumps, the whoops section….etc.The amount of abuse that a chassis goes through in off-road in just a race weekend would probablyfar exceed what an on-road chassis would see in its life time.Thus we decided an aluminum chassis as a backbone for our LCG conversion kit would be a better choice.Another great benefit of aluminum chassis is it helps in dissipating heat from your motor, battery and electronics. One more benefit of aluminum as a material for chassis is that it is a bit heavier than graphite.That’s right, in this case, heavy is good…especially when it is at the lowest part of the truck.From our testing it tends to give the truck more stability over the rough stuff and the truck doesn’t get “upset” as easily over the whoops and bumps.

2) 2.5mm thick graphite upper deck.Wait, didn’t we just say graphite is not good?Well, that was for the lower chassis.For the upper deck, because our lower deck is a solid 4mm thick aluminum, the amount of flex you will see would be almost next to none, so while the upper deck serves a purpose of providing overall rigidity, its main purpose in this LCG chassis kit is to align the front and rear gear box and secure everything in between, from the steering posts, to the chassis posts, to the motor mount, while keeping things light towards the top of the chassis

3) Cam type adjustable motor mount.We first incorporated this idea to help solve the motor mount issue with the Axial EXO Buggy.It worked out very well for that platform so we thought we incorporated into this LCG kit.It provides a really easy way to adjust the gear mesh for your truck and the motor screws can be accessed vertically instead of horizontally (through the back bumper and suspension linkages….which makes it really tricky).Just two screws from the top, and you can remove the motor cam to inspect the motor without loosing your gear mesh location.

We also spelled out the following specifics for the electronics

1) Adjustable battery positions.Battery being the heaviest electronics component on the truck can play a huge role in your truck’s handling characteristics if you can adjust its position on the chassis.We incorporated 3 different locations for battery adjustment to provide more setup options for racers.

2) Laydown steering servo.We want everything on the truck to be low and flat on the chassis, including the servo.

3) Everything towards the middle.We want the chassis to be as narrow as possible, tucking everything close to the center line.This will make for a narrow chassis thus less likely to scrape the ground during hard cornering or on rough tracks.It will also allow the truck to have faster transition in tight left right turns.

With the CAD drawing looking a lot closer to what we wanted, we moved on to the next step of the process…..Prototyping.